Most current mechanical watches use a balance/balance spring resonator as the time base. However, this device, proven for centuries, has pivots which rub against their bearing. Nowadays, micro-fabrication techniques make it possible to envisage replacing the balance/balance spring with a strip resonator. This makes it possible to eliminate friction from the pivots. Such a strip resonator is characterized by the fact that the strips fulfil both the bearing function and the elastic return force function. U.S. Pat. No. 9,207,641 in the name of CSEM presents such a resonator.
Unfortunately, in the event of a shock to the watch, the strips of the strip resonator, which are thin and slender, are liable to break.
EP Patent Application 3035127A1 by the same Applicant discloses a timepiece oscillator comprising a resonator formed by a tuning fork, which includes at least two mobile oscillating parts, fixed to a connection element by flexible elements whose geometry determines a virtual pivot axis of determined position with respect to a plate, and about which oscillates the respective mobile part, whose centre of mass coincides in the rest position with the respective virtual pivot axis. For at least one mobile part, these flexible elements are formed of crossed elastic strips at a distance from each other in two parallel planes, and whose directions, in projection onto one of said parallel planes, intersect at said virtual pivot axis of the mobile part.
EP Patent Application 3054356A1 by the same Applicant discloses a timepiece resonator comprising at least one weight oscillating with respect to a connection element fixed to a movement structure. This weight is suspended to the connection element by crossed elastic strips which extend at a distance from each other in two parallel planes, and whose projections onto one of the planes intersect on a virtual pivot axis of the weight, and define a first angle which is the vertex angle opposite which extends the portion of the connection element located between the attachments of the crossed strips to the connection element. This vertex angle is comprised between 68° and 76° for optimum isochronism.